Patches for imwrite

[John Swensen]

Here are three patches to fix/enhance three items in imwrite.  I don't know if 
you want me to create a bug report for each so they can be attached to a bug 
report. I suppose the quantumcheck patch can close out Bug #30715.  It doesn't 
necessarily solve the problem, but it does tell the user why it is happening 
and how to fix it themselves (recompile *Magick with higher quantumdepth).  I 
currently don't have write access to the main repository (and am not even sure 
I trust myself yet to have it), so someone else will need to apply these.

magick_gray_bitdepths.diff      - Fixes several problems with writing 2 bit and 
16 bit image formats
magick_formatlist.diff                  - Performs a query to the *Magick 
library the first time imwrite is called to determine the supported formats
magick_quantumcheck.diff        - Performs a check on QuantumDepth the first 
time maybe_initialize_magick is called and warns if it is less than 32 bits

Let me know if you need any changes and I will make additional modification.  I 
have finally forced myself to learn Mercurial queues and they are quite nice 
for switching between working on different bugs and patches.

John Swensen

magick_quantumcheck.diff
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magick_formatlist.diff
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magick_gray_bitdepths.diff
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